Solution of problem N3964 probability theory total prob

Solution of problem N3964 probability theory total prob

3964. Electric bulbs entering the store are manufactured at three plants. The first plant produces 60% of the total number of light bulbs, the second 25% and the third 15%. The production of the first plant contains 85% of standard lamps, the second 90% and the third 70%. What is the probability that a lamp purchased in the store is standard?

Additional information:

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)